Many of today's passenger vehicles and small trucks utilize powertrains having an engine and a multi-speed planetary transmission. The multi-speed planetary transmission generally includes a torque converter input mechanism, a multi-speed planetary gear unit, and a final drive unit. The multi-speed planetary gear unit generally has a plurality of torque-transmitting mechanisms that are hydraulically applied to establish gear ratios. In an interchange from one gear ratio to another, at least one torque-transmitting mechanism is disengaged while another is engaged. During ratio interchange and the engagement and disengagement of the torque-transmitting mechanisms, a drive interruption is a characteristic that is noticeable by the vehicle operator as a not smooth ratio transition. In order to provide a smooth transition during interchanges, calibration of the torque-transmitting mechanisms is required.
In many of the powertrains in use today, an electronic control mechanism is used to control the interchange and engagement of the various torque-transmitting mechanisms within the transmission. The electronic control mechanism includes at least two variable solenoid mechanisms, which supply the signals to provide the pressure to the torque-transmitting mechanisms, which are fluid-operated devices.
The electronic control mechanisms in use today generally include what is known as an adaptive portion of the transmission, which is operable to effect changes in torque-transmitting mechanism engagement and disengagement when a shift interchange is not proper. Most of the transmissions in use today have a learning feature within this adaptive portion, which rapidly adjusts the engagement and disengagement procedures of the transmission during the first period of operation after the vehicle has been placed on the road and in service. Thus, the initial calibrations that occur can produce ratio interchanges that are disturbing to the operator and may result in the vehicle being returned to a dealer for transmission correction, which is not necessary since the adaptive system will eventually correct the engagement sequence to be significantly improved.